Generally, a light emitting diode (LED) has attracted considerable attention as an environmentally friendly light source in various fields since it causes no pollution. Recently, the usage range of an LED has extended to various fields such as interior and exterior illumination, automobile head lights, and back-light units (BLUs) of displays, and thus an LED having high efficiency and excellent heat emission characteristics has been required. In order to obtain a high-efficiency LED, primarily, the raw material and structure of an LED must be improved, but, additionally, the raw material and structure of an LED package must also be improved.
High heat is generated from such a high-efficiency LED. Therefore, when high heat is not effectively discharged to the outside thereof, the temperature of the LED rises, and thus the characteristics thereof deteriorate, thereby reducing the lifetime thereof. For this reason, efforts have been made to effectively discharge the high heat emitted from a high-efficiency LED to the outside thereof.
Hereinafter, various kinds of elements emitting light, including an LED, are referred to as “optical elements”, and various kinds of products including one or more optical elements are referred to as “optical devices”.
FIGS. 1A to 1D are perspective views explaining a method of manufacturing a conventional optical device with respect to each process. First, as shown in FIG. 1A, in order to form a substrate 10 for mounting a conventional optical element, conductive plates 11, such as copper plates, having a predetermined thickness and insulating plates 12, such as glass plates or epoxy plates, having a predetermined thickness are alternately attached to each other in a plane direction, thus forming a laminate 13 (refer to FIG. 1B). Here, the attaching of the conductive plates 11 and the insulating plates 12 may be conducted by an adhesive or by thermo-compression bonding.
Next, as shown in FIG. 1B, when the laminate 13 is cut by a predetermined width in a direction perpendicular to the plane of the conductive plate 11, that is, in a vertical direction, a substrate 10, configured such that band-shaped conductive portions 10a and insulating portions 10b are alternately disposed, is obtained, as shown in FIG. 1C.
Next, as shown in FIG. 1D, LED chips 2 are disposed and mounted on each of the conductive portions (10a-{circle around (1)}, 10a-{circle around (2)}, 10a-{circle around (3)}) of the substrate 10 in a matrix form having regular intervals, and wires 3 are drawn out from each row of the conductive portions (10a-{circle around (1)}, 10a-{circle around (2)}, 10a-{circle around (3)}) and connected to the next row of the conductive portion 10a to obtain an LED array. The obtained LED array is molded with a transparent molding resin to prepare a plate-shaped LED array.
Meanwhile, the prepared plate-shaped LED array is configured such that its rows are electrically connected in parallel to each other and its lines are electrically connected in series to each other. In this case, this plate-shaped LED array may be directly made into a product or may be made into a product after it is separated along a row or line or is separated with respect to each piece. Moreover, when this plate-shaped LED array directly is used, it may be mounted on a metal printed circuit board (PCB) or may be provided thereunder with a heat sink.
FIG. 2 is a schematic perspective view showing a conventional optical device including a plurality of optical elements. As shown in FIG. 2, for example, in order to drive the plate-shaped LED array 20 prepared by the method of FIG. 1, there are required a driving circuit including passive elements 30, such as a resistor and a condenser, and a driving IC 40 serving to supply static current to the plate-shaped LED array 20; and a power supply circuit 60 such as switching-mode power supply (SMPS). A conventional optical device is configured such that at least one of a driving circuit and a power supply circuit is separately provided and then connected to a plate-shaped LED array substrate 10 through a power cable 50. Therefore, the conventional optical device is problematic in that its total size becomes large and its treatment and control is not easy.